Anatomic-radiological feasibility of transorbital magnetic resonance imaging-guided laser interstitial thermal therapy (MRIgLITT) for amygdalohippocampectomy in refractory epilepsy

OBJECTIVE : to study the anatomical feasibility of laser fiber insertion for interstitial thermal therapy via transorbital approach to the temporo-mesial structures (amygdala-hippocampus-parahippocampus complex) METHODS: Anatomical dissections were performed on two human cadaveric heads via a transorbital approach, in which screws and laser fibers were used for magnetic resonance imaging-guided laser interstitial thermal therapy (MRIgLITT) assisted by neuronavigation. In addition, eight transorbital trajectories were simulated using the transorbital entry points obtained from a cadaveric radiological study of four patients previously operated on for mesial temporal lobe epilepsy. RESULTS: The placement of all four laser fibers was successfully achieved in the anatomical specimens according to the established plan, with an average vectorial error of 1.3 ± 0.2 mm, and a complete coverage of the amygdala-hippocampus-parahippocampus complex. In addition, safe vascular trajectories were confirmed in the simulations of live patient trajectories. We found an ideal transorbital entry area in the inferolateral quadrant of the orbit, on the lateral wall of the orbit, over the greater wing of the sphenoid, between 15 and 20 mm lateral to the superior portion of the inferior orbital fissure, and between 5 and 10 mm superior to the inferior portion of the inferior orbital fissure. CONCLUSIONS: Placement of a transorbital laser fiber for MRIgLITT of the temporomesial structures for epilepsy is feasible; however, the small size of the laser fiber-anchoring screw currently precludes its use in clinical practice.